当我点击 PopupMenuButton 时，PopupMenuItems 没有显示

Question

我正在制作一个 flutter 应用程序，我有一个 PopupMenuButton.

当我点击 PopupMenuButton 时，PopupMenuItems 没有显示。这是代码：

class _ConfigurationListScreenState extends State < ConfigurationListScreen > {
    // const ConfigurationListScreen({Key? key}) : super(key: key);
    dynamic dataJson;

    @override
    Widget build(BuildContext context) {
      var configurationListChannel =
        ConfigurationListChannel(downlink: updateListData);
      configurationListChannel.requestConfigurationList();
      final GlobalKey _menuKey = GlobalKey();

      final button = PopupMenuButton(
        key: _menuKey,
        itemBuilder: (_) => < PopupMenuItem < String >> [
          PopupMenuItem < String > (child: Text('Doge'), value: 'Doge'),
          PopupMenuItem < String > (child: Text('Lion'), value: 'Lion'),
        ],
        onSelected: (_) {});
      return Scaffold(
        appBar: AppBar(
          title: Text("Configuration List"),
        ),
        body: Container(
          padding: EdgeInsets.all(20),
          child: ListView.builder(
            itemCount: dataJson.length,
            itemBuilder: (BuildContext context, int index) {
              return Card(
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: [
                    Container(
                      padding: EdgeInsets.all(16),
                      child: Column(
                        children: [
                          updateText('device_id', index),
                          updateText('downlink_value', index),
                          updateText('downlink_desc', index),
                          updateText('downlink_status', index),
                          updateText('sent_date', index),
                          updateText('created_date', index),
                        ],
                      ),
                    ),
                    Container(height: 150, color: Colors.red, child: button, alignment: Alignment.topRight, )
                  ],
                ));
            },
          ),
        ),
      );
    }

Answer 1

你好 Sagar 我认为你的 PopUpMenuItem 没有指定子项，所以它是不可见的。只需尝试将图标添加到它的子项。

final button = PopupMenuButton(
    key: _menuKey,
    child: Icon(Icons.menu)
    itemBuilder: (_) => < PopupMenuItem < String >> [
        PopupMenuItem < String > (child: Text('Doge'), value: 'Doge'),
        PopupMenuItem < String > (child: Text('Lion'), value: 'Lion'),
    ],
    onSelected: (_) {}
);

Answer 2

我不知道你为什么需要 GlobalKey。但是您试图在列表中多次使用 PopupMenuButton 和相同的全局键。这导致了问题，您不能在小部件树中有重复的全局键。因此，如果没有添加全局键，菜单项可以正常工作。这是您的工作代码片段，但我删除了与问题无关的部分。

Widget build(BuildContext context) {
      final button = PopupMenuButton(
        itemBuilder: (_) => < PopupMenuItem < String >> [
          PopupMenuItem < String > (child: Text('Doge'), value: 'Doge'),
          PopupMenuItem < String > (child: Text('Lion'), value: 'Lion'),
        ],
        onSelected: (_) {});
      return Scaffold(
        appBar: AppBar(
          title: const Text("Configuration List"),
        ),
        body: Container(
          padding: const EdgeInsets.all(20),
          child: ListView.builder(
            itemCount: 3,
            itemBuilder: (BuildContext context, int index) {
              return Card(
                child: 
                   Container(
                     height: 150, 
                     color: Colors.red, 
                     child: button, 
                     alignment: Alignment.topRight,
                   )
                );
            },
          ),
        ),
      );
    }

您介意解释一下全局密钥的用途吗？如果你需要它们，你应该为你的每个按钮准备一个唯一的按钮。不仅仅是列表中使用的一个按钮。但当您可能需要它们时，这并不常见。

当我点击 PopupMenuButton 时，PopupMenuItems 没有显示

When i click on PopupMenuButton, PopupMenuItems are not Showing

dart

flutter